<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
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                border:1px solid black;
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</head>
<body>
        <canvas width=400 height=600 id="cas"></canvas>
        <script>
              var cas = document.getElementById("cas");
        var ctx = cas.getContext("2d");
        ctx.arc(cas.width/2 + 100,cas.height/2,50,0,2*Math.PI);
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</body>
</html>